Since a liquid crystal display (LCD) device has characteristics of light weight, thinness and low power consumption, LCD devices have been widely used as a substitute for cathode rat tube (CRT) devices.
The LCD device uses the optical anisotropy and polarization properties of liquid crystal molecules to display images. The liquid crystal molecules have orientation characteristics resulting from their thin and long shape. An arrangement direction of the liquid crystal molecules can be controlled by applying an electrical field to the molecules. The LCD device including a thin film transistor (TFT) as a switching element is referred to as an active matrix LCD (AM-LCD) device, and has characteristics of high resolution and displaying moving images. Since the LCD device includes the TFT as the switching element, it may be referred to a TFT-LCD device.
FIG. 1 is an exploded perspective view of a conventional LCD device. The LCD device includes first and second substrates 12 and 22, and a liquid crystal layer 30. The first and second substrates 12 and 22 face each other, and the liquid crystal layer 30 is interposed therebetween.
The first substrate 12 includes a gate line 14, a data line 16, a TFT “Tr”, and a pixel electrode 18. The gate line 14 and the data line 16 cross each other such that a region is formed between the gate and data lines 14 and 16 and is defined as a pixel region “P”. The TFT “Tr” is formed at a crossing portion between the gate and data lines 14 and 16, and the pixel electrode 18 is formed in the pixel region “P” and connected to the TFT “Tr”.
The second substrate 22 includes a black matrix 25, a color filter layer 26, and a common electrode 28. The black matrix 25 has a lattice shape to cover a non-display region of the first substrate 12, such as the gate line 14, the data line 16, the TFT “Tr”. The color filter layer 26 includes first, second, and third sub-color filters 26a, 26b, and 26c. Each of the sub-color filters 26a, 26b, and 26c has one of red, green, and blue colors “R”, “G”, and “B” and corresponds to the each pixel region “P”. The common electrode 28 is formed on the black matrix 25 and the color filter layers 26 and over an entire surface of the second substrate 22. As mentioned above, the arrangement of the liquid crystal molecules is controlled by an electric field between the pixel electrode 18 and the common electrode 28 such that an amount of transmitted light is changed. As a result, the LCD device displays images.
Though not shown in FIG. 1, to prevent the liquid crystal layer 30 from leaking, a seal pattern may be formed along edges of the first and second substrates 12 and 22. First and second alignment layers may be formed between the first substrate 12 and the liquid crystal layer 30 and between the second substrate 22 and the liquid crystal layer 30. A polarizer may be formed on an outer surface of the first and second substrates 12 and 22.
An LCD device includes a backlight assembly opposing an outer surface of the first substrate 12 to supply light to the liquid crystal layer 30. When a scanning signal is applied to the gate line 14 to control the TFT “Tr”, a data signal is applied to the pixel electrode 18 through the data line 16 such that the electric field is induced between the pixel and common electrodes 18 and 28. As a result, the LCD device produces images using the light from the backlight assembly.
Generally, a glass plate is used for the first and second substrates 12 and 22. However, recently, a flexible plate, such as a plastic plate, is used for the first and second substrates 12 and 22 because the flexible plate is lighter and more flexible than the glass plate.
However, since a process of fabricating an array substrate is performed under a temperature higher than about 200° C., it is difficult for the flexible plate to be substituted for the glass plate. When the semiconductor layer is formed of one of amorphous silicon and polycrystalline silicon under a lower temperature than about 200° C., properties of the TFT are deteriorated. So, the array substrate is made of the glass substrate, and the color filter substrate is made of the flexible substrate.